The APM Body of Knowledge+ is a growing resource from the Association for Project Management featuring definitions, discussions, case studies and articles on all areas of projects, programmes and portfolios.

Resource scheduling

Resource scheduling is a collection of techniques used to calculate the resources required to deliver the work and when they will be required.

General

There are two broad categories of resource – consumable and re-usable. Scheduling these resources ensures:

efficient and effective utilisation;

confidence that the schedule is realistic;

early identification of resource capacity bottlenecks and conflicts.

The resource scheduling process has three steps:

allocation;

aggregation;

scheduling.

Allocation involves identifying what resources are needed to complete the work. In the case of consumable resources it is simply the quantity required. In the case of re-usable resources it is the total effort required and the number of individual resources.

Once time scheduling and resource allocation are complete, the resources can be aggregated on a daily, weekly or monthly basis as appropriate. The aggregated data is usually presented in a histogram that illustrates the fluctuating use of resources against time. In the case of consumable resources a cumulative curve (which usually takes the form of an ‘s-curve’) is also used to show the total amount consumed at any point in time.

Few re-usable resources are limitless, so the time schedule has to be adjusted to take into account the limited availability of resources over time. There are two approaches to reconciling resource limits and time constraints; resource smoothing (or time limited resource scheduling) and resource levelling (or resource limited scheduling).

Resource smoothing is used when the time constraint takes priority. The objective is to complete the work by the required date while avoiding peaks and troughs of resource demand.

A smoothed resource profile will be achieved by delaying some work. This will remove some flexibility from the schedule and its ability to deal with unavoidable delays, but the advantage is usually a more efficient and cost-effective use of resources.

Resource levelling is used when limits on the availability of resources are paramount. It simply answers the question ‘With the resources available, when will the work be finished?’

In many situations a mixture of levelling and smoothing may be required. This is particularly true in the programme and portfolio dimensions.

Other factors that can be considered include cost-efficiency measures, such as ‘just-in-time’ material deliveries; risks affecting resource availability; and the effect of learning curves on performance.

The fully-resourced schedule has to be achievable and have the support of the management team. Unless the team has input into the schedule, this support is likely to be limited at best and withheld at worst.

Resource scheduling may well reveal that the original target, calculated through time scheduling, cannot be achieved. This must be explained to senior management so that expectations can be managed. A fully resourced schedule, taking into account all constraints, will support the case for an extension of time or budget. Without it any case will be less substantial and unlikely to be accepted.

Project

The network analysis models used in time scheduling can be used to perform equally detailed calculations for resource levelling and resource smoothing.

Software packages perform very sophisticated calculations that can result in schedules being significantly changed. The danger with these calculations is that they make cause and effect difficult to determine. For example, if a resource levelling calculation is done that takes limits on five different resources into account and delays the project by a significant amount, it will be virtually impossible to see which resource had the greatest impact.

It should also be borne in mind that concepts such as the critical path and float have little meaning after a resource scheduling calculation has been applied.

An alternative to creating networks based on activity dependencies is to use a technique called critical chain. This method considers the availability of resources and the interdependencies between resources. Once a suitable resource is developed, ‘buffers’ of spare time are allowed at the end of each path. Monitoring the rate of usage of the buffer time is key in controlling projects based on critical chain.

Programme

The projects and change management activity within a programme will have varied requirements for resource scheduling. The programme management team must decide how resources will be scheduled in each context.

On some projects (or parts of projects) the programme manager may impose time constraints that require the resource schedule to be smoothed. On others, resource constraints may be imposed that require the schedule to be levelled.

The programme and its use of resources are a highly dynamic and complex environment. Successful resource scheduling will depend upon a close working relationship between the programme manager, project managers and business change managers, who all put the needs of the programme ahead of individual projects and change management activity.

A strong programme-support function is vital. Specialist planners (schedulers) will aggregate information from around the programme to show the overall resource profile and assist in evaluating decisions about the allocation of resources and potential bottlenecks.

Portfolio

In general management usage, capacity planning is defined as ‘the maximum amount of work that an organisation is capable of completing in a given period ’. Capacity planning, in this sense, also applies to portfolios.

In the portfolio domain, resource scheduling is done at a very high level. It is not so much about the timing of resource usage as ensuring that the overall capacity is compatible with the amount of work to be done.

The portfolio practice of categorisation helps break the problem down. Prioritisation shows where resources need to be focused and resource demand is one of the factors taken into account when balancing the portfolio.

A portfolio support function should ensure that projects and programmes produce information that can be aggregated in a consistent and timely manner, enabling the portfolio manager to make informed decisions.